Fat embolism is a significant cause of post-traumatic morbidity and mortality, often occurring in healthy young adults as a complication of fractures which in themselves are not life threatening. Although numerous theories have been advanced to explain the origin of the particles associated with fat embolism, their source is still in question; and subsequently there is no generally accepted effective therapeutic program for this condition. We propose a prospective controlled study of patients sustaining multiple fractures, making use of a variety of techniques to evaluate the nature and source of the lipid particles and associated proteins present in the sera of patients with clinical syndrome of fat embolism. The detailed studies described in the research proposal are aimed at clearly defining the nature and source of the embolic fat. Techniques have been developed which permit the isolation of the abnormal lipid particles during the critical post-traumatic period. These will be analyzed by chromatographic, electrophoretic, and ultracentrifugal techniques to establish their lipid, lipoprotein, and protein composition. Immunologic methods will be used to establish the tissue source of the protein moieties of the embolic particles. Our long-range goal is to establish a detailed understanding of the lipid and protein abnormalities associated with this syndrome, to provide a base of controlled data from which effective therapeutic measures might be developed.